In the electronics industry, the tendency has been to reduce the size of electronic devices such as camcorders and portable telephones while increasing performance and speed. Integrated circuit packages for complex systems typically are comprised of a multiplicity of interconnected integrated circuit chips. The integrated circuit chips usually are made from a semiconductor material such as silicon or gallium arsenide. The integrated circuit chips may be mounted in packages that are then mounted on printed wiring boards.
Packages including integrated circuit chips typically have numerous external pins that are mechanically attached by solder or a variety of other known techniques to conductor patterns on the printed wiring board.
Typically, the packages on which these integrated semiconductor chips are mounted include a substrate or other chip-mounting device. One example of such a substrate is a leadframe. Leadframes also typically include at least an area on which an integrated circuit chip is mounted and a plurality of power, ground, and/or signal leads to which power, ground, and/or signal sites of the integrated semiconductor chip are electronically attached. Semiconductor integrated chips may be attached to the leadframe using adhesive or any other techniques for attaching such chips to a leadframe which are commonly known to those skilled in the art, such as soldering. The power, ground and signal sites on the chip may then be electrically connected to individual leads of the leadframe.
Leadframes have been used extensively in the integrated circuit packaging industry mainly because of their low manufacturing cost and high reliability. Leadframe packages remain a cost-effective solution for packaging integrated circuits and in recent years certain variations of leadframes such as leadless packages also emerge as improvements.
Typical leadframe packages include a die attach paddle, or pad, surrounded by a number of leads. The leads are temporarily attached to the die attach paddle. An integrated circuit chip, is attached to the die attach paddle using a conductive adhesive such as silver epoxy. The conductive adhesive is cured after die attach. After the die is attached to the die paddle, a wire-bonding process is used to make electrical interconnections between the integrated circuit and the leads of the leadframe. After wire bonding, the leadframe with the integrated circuit attached is encapsulated using a molding compound.
Such enclosures may include encapsulant in a plastic or a multi-part housing made of plastic ceramic, or metal. The enclosure protects the leadframe and the attached chip from physical, electrical, and/or chemical damage. Finally, post mold curing and singulation steps are conducted to complete the packaging process.
The leadframe and attached chip(s) may then be mounted on, for example, a circuit board, or card along with other leadframes or devices. The circuit board or card may then be incorporated into a wide variety of devices such as computers, automobiles, and appliances, among others.
As integrated circuits have become smaller with increased performance capabilities leadframes for integrated circuits have been adapted to accommodate these integrated circuits. A multi row leadframe has found increased use to provide additional leads on a leadframe of a given size. The multi row leadframe includes an outer row of leads and one or several inner rows of leads surrounding a die pad to which the integrated circuit die is attached. The contact pads on the integrated circuit are connected to the inner and the outer rows of leads with bonding wires in accordance with the particular design of the semiconductor package.
One problem that persists with multi row leadframes is that separation of the leads from the leadframe so as to electrically insulate each contact from each other is complex and cumbersome. Such complexity of the separation process also adds risk to the reliability of the resulting chip packages.
Another problem with multi row leadframes is that the die pad must be in a different plane from the plane on which the outer row leads are placed. This non-planar nature of previous leadframes is to prevent the cutting of the outer row leads during the process of separating the inner row leads from the leadframe and it adds additional complexity to the leadframe design as well as to the separation process.
Thus, a need still remains for reducing the complexity of the leadframe design and the separation process. In view of the ever-increasing commercial competitive pressures, along with growing consumer expectations and the diminishing opportunities for meaningful product differentiation in the marketplace, it is critical that answers be found for these problems. Additionally, the need to reduce costs, improve efficiencies and performance, and meet competitive pressures, adds an even greater urgency to the critical necessity for finding answers to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.